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How alcohol content in dry-hopped beer affects final beer composition – a model study
S. Cocuzza, S. Gmeinwieser, K. Helmschrott, F. Peifer and M. Zarnkow

The technique of dry hopping is used to produce many different beer styles with various alcohol contents. Information about the alcohol-dependent behaviour of hop components after dosing is crucial to control the resulting flavour and ensure consistent beer quality. This systematic pilot-scale study was therefore performed using standardised procedures by only varying the alcohol content in the beer samples in four steps from 0.5 % to 10.5 % alcohol by volume (ABV). A commercially available alcohol-free wheat beer was used as a base beer to adjust the alcohol concentrations while keeping the hop dosing rate consistent at 250 g/hl using Type 90 Pellets of the variety Solero. After a semi-static contact time of 14 days, the following attributes were analysed: hop-derived bitter and aroma compounds, polyphenol content, nitrates, foam stability and pH value. The conclusions for the non-volatile attributes are as follows: iso-alpha acids, humulinones, polyphenols and foam stability remained unchanged with varying ABV. In contrast, increasing the alcohol content improved the transfer and solubility of hydrophobic alpha and beta acids as well as xanthohumol, resulting in higher concentrations. Increasing the alcohol also caused lower quantities of nitrates to be transferred. Foam stability was negatively affected when more ethanol was added, but this drop in stability was compensated by more foam-positive alpha acids introduced. The beer pH showed very little increase and was hardly influenced by the ABV. For the hop-derived volatile substances, the conclusions are as follows: The terpene alcohols displayed very good solubility with the ABV having hardly any impact. The transfer of hop esters was only somewhat ABV-dependant and the presence of alcohol above 0.5 % further increased the solubility to finally reach a certain plateau. Ketone concentration did depend on the ABV. Mono- and sesquiterpenes are most clearly influenced by the alcohol content and the highest concentrations were reached at the highest ethanol addition.

Descriptors: dry hopping, alcohol content, transfer rates, solubility behaviour of hop bitter and aroma components, polyphenols, nitrates, foam stability, pH value

BrewingScience, 75 (May/June 2022), pp. 44-53